Ammonium nitrate explosive with polyurethane resin prepared from nitric acid partial esters



United States Patent Ofiice AMMONIUM NITRATE EXPLOSIVE WITH POLY-URETHANE RESIN PREPARED FROM NITRIC ACID PARTIAL ESTERS Harold F. Bluhm,Tamaqua, Pa., assignor t Atlas Chemical Industries, Inc., Wilmington,Del., a corporation of Delaware No Drawing. Original application Sept.17, 19 62, Ser. No. 224,244, now Patent No. 3,256,214. Divided and thisapplication Apr. 13, 1966, Ser. No. 565,342

' 2 Claims. (Cl. 149-8) This is a division of application Serial Number224,244, filed September 17, 1962 now Patent No. 3,256,214.

The present invention relates to a new type of explosive and inparticular, to explosive resins comprised of crosslinked thermosettingpolymers in which the explosive property is provided by nitric acideater groups contained in a three-dimensional polymer system.

The resin products of the present invention are suited to be cured atroom temperature. The products may be cast or molded to form explosivematerial in various shapes. The present products may be foamed to formlow density explosive materials. The present products are useful as amatrix for other explosive materials and as a sensitive, water resistantcoating for ammonium nitrate.

According to the present invention, a polyurethane resin is providedwhich contains at least about 4.5% by weight of nitrogen in the form ofnitric acid eater groups. The polyurethane resin compositions of thepresent invention may be compounded by condensing a reaction mixture ofa polyisocyanate with a compound furnishing hydrogen reactive with anisocyanate and containing a suflicient number of nitric acid eatergroups to introduce at least about 4.5% by weight of nitrogen in theform of nitric acid ester nitrogen into said resin. The polyurethaneresin compositions of the present invention may be compounded bycondensing a reaction mixture of a polyisocyanate with either a nitricacid partial ester of a polyhydroxy compound, a nitric acid ester of anamino alcohol, or mixtures thereof, wherein the reaction mixtureincludes a component containing at least two radicals supplying hydrogenreactive with an isocyanate.

Suitable polyisocyanates which may be employed are: the diisocyanatessuch as hexamethylene diisocyanate, paraphenylene diisocyanate,metaphenylene diisocyanate, 4,4 diphenylene diisocyanate, 1,5 napthlenediisocyanate, 4,4 diphenylene methane diisocyanate, the toluenediisocyanates, 4,4 diphenyl ether diisocyanate, 3,3 dimethyl 4,4diphenyl diisocyanate, and 3,3 dimethoxy 4,4 diphenyl diisocyanate; thetriisocyanates, such as 4,4,4- triphenyl methane triisocyanate, and2,4,6, toluene triisocyanate, and the tetraisoyanates such as 4,4dimethyl diphenyl methane 2,2, 5,5 tetraisocyanate. Mixtures ofcompatible polyisocyanates may also be used. Because of availability andprice the toluene diisocyanates such as the 2,4 toluene diisocyanate,2,6 toluene diisocyanate, and blends of these diisocyanates areparticularly preferred.

It will be noted that the reaction mixtures of the present inventioninclude a polyisocyanate, a nitric acid eater and a component containingat least two radicals supplying hydrogen reactive with an isocyanate.The nitric acid eater may be the component that supplies the tworeactive hydrogen radicals or the two reactive hydrogen radicals may besupplied by an additional component.

If a nitric acid partial ester of a polyhydroxy compound containing atleast two available hydroxyl groups is utilized, a resin of the presentinvention may be prepared by condensing such an ester with apolyisocyanate. Suitable 3,309,247 Patented Mar. 14, 1967 nitric acidpartial esters of polyhydroxy compounds which contain at least twoavailable hydroxyl groups, for example, are: mannitol triandtetranitrates, sorbit-ol triand tetranitrates, and anhydroenneaheptitoldinitrate.

If desired, a nitric acid ester having a single reactive hydrogen may beutilized. In such case, a third component having at least two reactivehydrogen radicals is required. The third component or crosslinking agentis adapted to become part of the resin matrix through a reactivehydrogen linkage with the nitric acid ester and the polyisocyanate.Suitable nitric acid esters having a single reactive hydrogen, forexample, are: compounds having a single available hydroxy group such as,mannitol pentanitrate, sorbitol pentanitrate, and gylcerin dintrate. Thethird component requires two or more available hydrogen radicalsreactive with an isocyanate group. Examples of compounds havingavailable hydroxyl groups and suited to use as the third component are,gylcerol, ethylene, gylcol, polyethylene glycol, 1,4-butane glycol,sorbitol, mannitol, 1,6-hexamethylene glycol, ethylene and propyleneoxide adducts of polyols.

In accord with the present invention, the reactive hydrogen ispreferably supplied by a hydroxy group. Reactive hydrogen may besupplied by phenolic hydroxyl, amino, thiol, sulfinic or sulfonic acidgroups, however the activity of such groups may undesirably speed thereaction resulting in an exothermic polymerization and fume-otf of thenitric acid ester groups.

The sensitivity and explosive properties of the resin products of thepresent invention are dependent upon the amount of nitrogen present inthe form of nitric acid ester groups. In order that the resin be impactsensitive, the present resins require at least about 4.5% by weight ofnitrogen in the form of nitric acid ester groups compared to the totalweight of the resin.

The resin compositions of the present invention may be prepared withouta catalyst by simply mixing the components and allowing the mixture toset at room temperature. The setting or curing reaction may be speededby warming. However, one of the advantages of the present invention isthat the resin may be cured at a low temperature, well within the limitsof stability of the nitric acid ester component. If a three componentsystem is utilized, a prepolymer mixture may be formed by initiallymixing the polyiso-cyanate component with the component supplying atleast two radicals containing hydrogen reactive with an isocyanate. Thenitric acid ester component may then be mixed with the prepolymermixture and resultant mixture cured.

In general, the resin compositions of the present invention require nocatalyst. However, the resin setting times may be speeded by theaddition of small amounts of amines to the resin mixture. Suitable aminecatalysts, for example, are diand triethanol amine, diethylene triamineand dimethyl aniline.

The resins of the present invention are useful, per se, as explosivesand as sensitive coating for ammonium nitrate blasting compositions. Theresins of the present invention are particularly suited to processesutilizing explosives which are extruded or cast in rigid or flexibleforms, such as metal forming processes. The present resins are alsouseful in the manufacture of booster and water resistant high explosivesin which the resin supplies a matrix for a blasting agent such asammonium nitrate or an explosive compound such as PETN (pentaerythritoltetranitrate) or RDX (cyclotrimethylene trinitramine).

The resin compositions of the present invention are eminently suited toproduce thermosetting foamed resin explosives. The foamed resinexplosives of the present invention may be formed by simplyincorporating a gas forming substance, such as water, in the resincomposition prior to the time the resin is cured.

The nature of the present invention is illustrated further by thefollowing examples, which however, should not be construed to limitunduly the generally broad scope of the invention.

EXAMPLE I A blend of an equal weight of anhydroenneaheptitol nitrate,containing 13.77% by weight of nitrogen, in the form of nitric acidester, and 2,4-toluene diisocyanate were blended together to form areaction mixture. N catalyst was added. The reaction product cured to ahard glass-like mass in 36 hours at normal room temperature. Thenitrogen content, in the form of nitric acid ester nitrogen, of theproduct was calculated to be 6.9% by weight. The resin was found to beimpact sensitive.

EXAMPLE II A blend of 29.6 parts by weight of mannitol tetranitrate and35.3 parts by weight of polyoxyethylene sorbitol was mixed with 35.3parts by weight of 2,4-toluene diisocyanate. No catalyst Was added. Thecomponents formed a clear, liquid reaction mixture. After 16 hours themixture cured to a hard-glass like resin which was found to be impactsensitive. The nitrogen content of the product, in the form of nitricacid ester nitrogen, was calculated to be 4.6% by weight.

EXAMPLE m A blend of 66.7 parts by weight of mannitol pentanitrate and4.9 parts by weight of ethylene glycol was mixed with 28.5 parts of2,4-toluene diisocyanate. The mixture was placed in an aluminum dish andwarmed by radiant heat to 50 C. After two hours, the resin cured to arubber-like polymer. The heat source was removed and the curingcontinued at room temperature. After 24 hours, the mixture cured to ahard glass-like resin which was found to be impact sensitive. Thenitrogen content, in the form of nitric acid ester nitrogen, wascalculated to be 11.5% by weight.

EXAMPLE IV The components of a resin in accord with Example II wereblended and a 3 parts by weight of particulate ammonium nitrate mixedtherein. No catalyst was added. The components formed a moldablereaction mixture containing particulate ammonium nitrate. After 16hours, the mixture cured to a hard glass-like resin which was found tobe impact sensitive.

EXAMPLE V i A tumbling barrel was charged with 100 parts by weight ofdry particulate ammonium nitrate and 3 parts by weight of the liquidresin prepared in accord with Example II. The mixture was tumbled for 18minutes at room temperature and one hour at 50 C. Tumbling was continuedfor one hour to cool the resin-coated particles. The resin coating hadcured to a hard glass-like finish on the surface of the ammonium nitrateparticles. The product was a water-resistant, resin-coated particulateammonium nitrate.

4 EXAMPLE v1 A prepolymer mixture consisting of one part by weight of 10polyoxyethylene sorbitol and 2 parts by weight of 2,4-toluenediisocyanate were heated at C. in the absence of moisture until theviscosity of the mixture increased sufficiently to prevent free flow ofthe prepolymer at room temperatures. This took about 1 hour heatingtime.

50 parts by weight of prepolymer formed as described in the precedingparagraph and 50 parts by Weight of mannitol pentanitrate were blendedwith one part by weight of silicone oil to obtain a viscous paste. Thepaste was slowly heated to a maximum of 70 C. while being agitated. Theagitation was continued until a free flowing liquid was produced. Themixture was then cooled to room temperature and one part by weight ofwater mixed therein. The mixture containing the added water was thenreheated to 70 C. An evolution of gas and a gradual increase inviscosity of the mixture was noted. The heating was continued until themixture became stringy and an additional part by weight of water added.The resin mixture was then allowed to foam at room temperature. Althoughthe foaming essentially ceased after about 2 hours, the raised resinremained tacky. After about 18 hours, a hard rigid foam was producedthat had expanded to about 10 times the original volume of the liquidresin. The resin product was found to burn violently and to be impactsensitive.

EXAMPLE VII The procedure of Example VI was repeated except that nosilicone oil was added and the second water addition was omitted. Afterabout 18 hours, the product cured to a hard rigid foam about 10 timesthe original volume of the liquid resin. violently and was found to beimpact sensitive.

What is claimed is:

1. An explosive material comprising particulate ammonium nitrateembedded in a matrix of a polyurethane resiq composition compounded bycondensing a reaction mixture of a polyisocyanate and a member of thegroup consisting of nitric acid partial esters of polyhydroxy compounds,wherein the reaction mixture includes a component containing at leasttwo radicals supplying hydrogen reactive with isocyanate.

2. An explosive material comprising particulate ammonium nitrate coatedwith a polyurethane resin composition compounded by condensing areaction mixture of a polyisocyanate and a member of the groupconsisting of nitric acid partial esters of polyhydroxy compounds,wherein the reaction mixture includes a component containing at leasttwo radicals supplying hydrogen reactive with isocyanate.

References Cited by the Examiner UNITED STATES PATENTS 3,132,976 5/1964Klager et al. l49l9 3,190,775 5/1965 Ender l498 3,245,849 4/1966 Klageret a1. l49l9 CARL D. QUARFORTH, Primary Examiner.

B. R. PADGETT, Assistant Examiner.

The resin product burned

2. AN EXPLOSIVE MATERIAL COMPRISING PARTICULATE AMMONIUM NITRATE COATEDWITH A POLYURETHANE RESIN COMPOSITION COMPOUNDED BY CONDENSING AREACTION MIXTURE OF A POLYISOCYANATE AND A MEMBER OF THE GROUPCONSISTING OF NITRIC ACID PARTIAL ESTERS OF POLYHYDROXY COMPOUNDS,WHEREIN THE REACTION MIXTURE INCLUDES A COMPONENT CONTAINING AT LEASTTWO RADICALS SUPPLYING HYDROGEN REACTIVE WITH ISOCYANATE.